Bora rims seem to be cracking...

[Alexandrumarian]

This morning I set to do some cleaning on my bike and noticed a ridge in between the front wheel spokes... Looked more closely and it is real bad: around several spokes it seems to be downright cracking. An uncracked ridge in the clear coat can be found over most of the rim, and it is also starting to form over a couple short sections on the rear wheel too.

These are summer bought wide Bora 35 One tubs, ridden for 2000km. Although I tried to be as careful as possible with new expensive wheels, they saw a number of unavoidable potholes but that is life. It doesn't help I weight 95Kg, so rather than bitching at Campy I should maybe bitch at my brain for not sticking with some sturdier alloy wheels.

The worst part is I might end up with these as wall decos. When gluing the tubs I sanded away the codes from the rim bed, also cleaned the external code stickers. I do have the warranty card with the serial number but if it is missing from the wheels I fear they will deny replacement.

In a very happy scenario it might only be the clearcoat bursting from stresses, with the carbon being actually OK. Still I would be more than reluctant to ride on them anymore.

[whosatthewheel]

Don't look like cracks to me. Bear in mind your composite is coated with a layer of lacquer, which is probably beginning to flake off... it's basically a cosmetic damage, the rim is sound

[Alexandrumarian]

Yes it is possible it is just the lacquer. Lacquer forms ridges, or flakes if the base material has movement, which might be expected in this very highly stressed part of the wheel, but it can also very well mean the base material is fractured too.

I would be very grateful if other owners of (well used) Boras could check theirs and see if there is a ridge on their wheels. It is easily view-able under the light angle, and easily felt with the finger.

Many thanks!


In the mean while I sent pics to the seller and asked if it is possible to get an exchange with the missing code stickers. If they say no I will remove the clear coat so I can have a better look at the actual carbon.

[Alexandrumarian]

Found a magnifier and looked inside a few of the flaked areas, fibers seem intact! I'm starting to suspect the lacquer ridge formed from expansion/contraction from braking heat (i've been down over anumber of descents, often over 10%)

Braking heat would also explain why it happened mostly on the front wheel.

[Valbrona]

If Bora's are made by gluing the two halves of the rim together, I would expect that the glue wasn't very strong.

[spud]

very true - drive side rear is where you would expect to see cracks, well before front spokes at lower tension, with no added dynamic tension.

[whosatthewheel]

If Bora's are made by gluing the two halves of the rim together, I would expect that the glue wasn't very strong.

The ridge is simply where the mould had its opening. Most likely the lacquer laso had to be cured and therefore it shows... I don't think the rims were "glued" together

[Alexandrumarian]

Yes rear wheel has a lot more concentrated tension, two ds and one nds spokes are grouped over a tight spot: 16, 12, 16 points on a park meter. Front spokes are 12-13 evenly spaced. I don't detect any loss of tension or trueness.

There might be a seam deeper down (bad idea imo) but the outer cloth is one piece with the fibers at 45 degrees. I stared at it for half hour and can't see any broken fibers. Actually fibers can be glanced over in one of the photos.

It is possible the lacquer ridge was there from the beginning and I simply did not notice it before. Now that it is flaking it grabs finger skin much more easily.

[Alexandrumarian]

.

[djgarrett21]

That is most definitely mark-off from the mold. Wheels are fine.

The mold for the wheels is in two halves. They get bolted together, some air pressure is added and then they are put in an oven. Sometimes resin can find its way to seams and pool a bit in that area. When the wheel is finished curing and the mold is removed you will get a little bit of resin right at the seam which in some cases is sanded down or simply knocked off or both. The nice uniform ridge right at the mid-plane if the wheel in your pictures is right where the seam is for the two halves of the molds. So what you're seeing is simply a resin rich area that got knocked off at the factory after the rim was removed from its mold.

[tommasini]

Yes totally fine - simply mold seams, not fiber seams or cracking. Oh BTW it make me cringe when someone calls the top coat “lacquer”. Here in the US lacquer is a very low flashpoint, very soluable (in many solvents), poor UV resistance and low durability finish. The campy and most other carbon rims will be finished in a much more resistive resin.

[spdntrxi]

ugly as it is .. mold seams.

[addictR1]

Where are Bora One or Ultra made?


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[Alexandrumarian]

Oh BTW it make me cringe when someone calls the top coat “lacquer”. Here in the US lacquer is a very low flashpoint, very soluable (in many solvents), poor UV resistance and low durability finish. The campy and most other carbon rims will be finished in a much more resistive resin.

colloquially "lacquer" is often used for any clear finish, although indeed in most cases it now refers to nitrocellulose indeed. But before nitro, it referred to Asian shellac or urushi, while varnish was mostly reserved for oil based concoctions (although sometimes "violin varnish" was often based on shellac and alcohol!)


Anyway after checking with a few people the ridge is indeed present from the start. What remains to be determined is if the chipping occurs later or it is simply a larger ridge that has broken when removing rim from mold.


My ID card doesn't seem to have a "made in" but the construction/assembly was surely in Romania or Italy. Where exactly the rims are made remains a bit of a mystery.

[djgarrett21]

The campy and most other carbon rims will be finished in a much more resistive resin.

colloquially "lacquer" is often used for any clear finish, although indeed in most cases it now refers to nitrocellulose indeed. But before nitro, it referred to Asian shellac or urushi, while varnish was mostly reserved for oil based concoctions (although sometimes "violin varnish" was often based on shellac and alcohol!)

There is no surface "finish" operation as you guys are talking - the surface you see is the molded surface of the part. It hasn't gone through some secondary operation after being cured.

Virtually all bicycle parts are fabricated from pre-preg, or carbon fibers which have been pre-impregnated with resin. The shiny surface of your wheels is actually considered "resin rich" which is to say that there is too much resin in the part and the resin has migrated to that surface. Not a huge deal and for bicycle parts such as wheels it is desired since that is usually what the customer wants.